Odor Management Plan development tool helps farmers deal with farm odor

Odors are customary when raising livestock. Having an Odor Management Plan that determines the sources of odors, identifies control practices and establishes a monitoring strategy help livestock farmers manage the smells associated with their farm.

Everyone has a unique reaction to odors but livestock odors are almost universally accepted as annoying and unpleasant. However, farm owners, who to varying degrees are anoxic to the smells on the farm, will find the odor much more tolerable than their friends from town who don’t have the same affiliation with and exposure to the farm odor. An Odor Management Plan (OMP) can help farmers assess the situation on their land and find solutions to the odor issue.

There are three reasons livestock farmers write an OMP:

  1. Odor management plans are a proactive step indicating the farm owner’s or manager’s concern for the farm’s rural neighbors.
  2. The farm has a history of odor concerns and either on their own, or at the request of a responding government agency, the farm management develops an OMP to identify odor sources and possible control practices.
  3. An OMP may be a required addition to a local or state permit application or site verification request for a new or expanding livestock operation.

Writing an OMP should provide an accurate analysis of the current farm status and provide direction in the event of future odor concerns or complaints. But developing an OMP should not be a challenging, time consuming experience. Michigan State University Extension has developed the OMP Template using an Excel spreadsheet. The template uses scroll-down boxes, embedded calculations and designate cells for user input to guide users through the development of the OMP. You can find these resources here

OMPs should consider five factors that impact odor or the perception of odor, including:

  • Identifying the farm’s major odor sources
  • Determining the magnitude of odor from each source
  • Identifying current and potential odor control practices
  • Establishing a plan for monitoring farm odors
  • Establishing a strategy for maintaining and enhancing community relations

Identifying major odor sources

Farm odors are emitted from three obvious sources; animal housing, manure storage and land application. While these three management categories are the areas of greatest concern other sources, if left unaccounted for, have the potential to make significant contributions to overall farm odor. The potential odors from temporary field stacking, stored feeds, the feed processing area and mortality handling also need to be addressed in the OMP.

Determining the magnitude of each odor source

The Minnesota Odors From Feedlots Setback Estimation Tool (OFFSET) provides resources for evaluating the magnitude of odors from animal housing and manure storage structures. Other factors contributing to total farm odor are evaluated using a “High,” “Medium” and “Low” designation based on the evaluation conducted by the person writing the OMP.

Charts contained in Minnesota OFFSET provide Odor Emission Numbers for most animal housing systems and manure storage structures. Also included in the tool are Odor Control Factors which are used to calculate the odor reduction provided by implementing proven odor mitigation practices.

By following OFFSET’s recommendation of multiplying the Odor Emission Number by the square feet of animal area or manure surface of each structure and, if odor control practices are in place, the Odor Control Factor then dividing by 10,000, users are able to calculate an Odor Emission Factor for each facility. Table 1 provides an illustration of using OFFSET to evaluate odors from the housing and manure facilities on a sample dairy farm.

Table 1: Using OFFSET to determine magnitude of odor

Odor Emission


Odor Control




Sq. Ft.



2 - free stall barns: 66’ x 373’





Dry cow barn: 40’ x 100’





Dry cow lot: 40’ x 100’





Heifer barn: 60’ x 80’





Earthen storage: 250’ x 350’





Heifer barn stockpile: 20’ x 30’





aFrom OFFSET’s chart of Odor Emission Numbers

bFrom OFFSET’s chart of Odor Control Factors 4” of natural crust equals an odor control factor of 0.4

The information provided by Table 1 helps farmers and farm managers recognize the odors generated by each source and, if needed, prioritize additional odor control practices. Additionally, by listing other odor sources and designating them as a “High,” “Medium” or “Low” concern in the OMP, may assist with determining additional odor control measures for those areas as well.

Identifying odor control practices

Table 1 provides an illustration of utilizing odor control practices. By encouraging minimal surface disruption the sample farmer is able to get 4 inches of a natural crust to form on the farm’s earthen storage. The OMP should recognize the impact of current odor control practices but also list potential odor control practices should monitoring indicate additional odor reduction is warranted.

Odor monitoring

Each of us has a unique response to farm odors. A defined odor monitoring strategy will warn the farm management of abnormal odors coming from the farm, help determine if odor complaints are a valid concern or overreaction by a sensitive neighbor and will evaluate the effectiveness of new odor control practices. Those recognized in the OMP as assisting with odor monitoring should be someone who is not exposed to the farm’s odors on a day-to-day basis and someone whose opinion the farm management respects and trusts.

Community activities

Communication can keep small problems from escalating into large concerns. The OMP should discuss those activities farmers and farm employees participate in that will enhance local and community relations. Suggestions include hosting farm picnics, providing neighbors meat or farm products during the holiday season, volunteering time to youth activities and serving on local government boards.

The OMP Template guides users through each of these steps. The Minnesota OFFSET calculations are embedded within the spreadsheet. Other odor sources are listed in scroll down menus and management strategies are suggested to establish the “High,” “Medium” and “Low” designation for each of the categories. Input boxes are provided for discussing odor monitoring and community activities. For more information on the template contact Jerry May at mayg@msu.edu.

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